Food drying method

ABSTRACT

The field of the invention is food drying apparatus and methods. In particular, the invention discloses a rotary dryer which dries food granules, such as rice, by rotation within a perforated cylindrical barrel, to prepare the rice for packaging. The dryer provides high velocity drying zones along its length, and high temperatures may be used.

This is a continuation of application Ser. No. 08/116,064, filed Sep. 2,1993, now abandoned.

BACKGROUND OF THE INVENTION

The invention relates to a method and apparatus for processingfoodstuffs; more particularly, this invention relates to methods andapparatus for processing rice to achieve a quick-cooking rice.

Mankind is continually searching for new and better methods of cookingcereal grains, vegetables and other foodstuffs. In large scalecommercial operations, the cooking of foodstuffs requires specialapparatus and specially adapted cooking methods that will provide auniform and desirable food product while at the same time handling largequantities of foods.

In the cooking of certain starch-containing foods such as vegetables andcereal grains, several problems are encountered. First, the foodgranules must be moved from storage tanks to processing vessels, and insome cases to holding tanks or cooking vessels, and then they may bedistributed to dryers to remove water from the food granules. Thephysical transport of the food granules during such processing must bewell regulated and maintained to achieve a desirable flow of foodparticles through the processing system from one processing step toanother, without undesirable clumping or aggregation of food granules.

In certain cases the physical handling and heat applied to grains duringcooking is designed to result in physical or chemical changes to thestarch or other molecules that are contained in the food stock itself.For example, in the cooking of cereal grains, such as rice, the goal isto gelatinize the starches in the grain. In such a process, loose starchmolecules may be leached out of the food granules or the starchmolecules may be ruptured as a result of handling or processing. If thatoccurs, then cooking processes may tend to glue together the granules,slowing advancement of the food product through the processing system.This "gluing" problem is particularly troublesome in the cooking of riceand, if allowed to proceed unabated, will cause the surface of riceparticles to stick together, causing large globules to form, makingfurther transport and processing of the rice impractical, if notimpossible.

In the past, the problem of "gluing" of food granules by the release orrupture of starch molecules could be controlled, at least to a limiteddegree, by using large amounts of fluid in transporting the food throughthe processing machinery, cookers, conduits, and the like. Typically,water is used as a transport fluid, and large amounts of water tend todilute the "glue" (free hydrated starch), thereby minimizing the adverseeffect of free starch. By using large amounts of water, cereal grainsmay be processed without the undesirable globules forming to slow thetransport of the grains through processing equipment. However, such useof water to dilute this gluing effect results in spent process waterwith large amounts of free starch which must be discarded or furtherprocessed such as by water treatment.

Unfortunately, many communities have greatly increased the fees thatcommercial users must pay for water in such food processing operations.As such, the processing of food wherein large amounts of water arerequired has become extremely expensive in these communities, and newerand better methods of transporting and cooking food in a processingsystem, while using less water, are highly desirable.

Also, in the past, water used in a food processing system for transportof food has been discarded as waste water at the point in the processingafter which the water is no longer needed for transport of the food.However, recent environmental regulations have greatly curtailed theamount of waste water and waste materials that may be disposed of byfood processing facility. Moreover, many public utilities and watercompanies charge corporate water consumers not only on the basis of theamount of water consumed, but also on the basis of the number of gallonsof waste water that is discharged back into the public sewer system.Therefore, it is desirable to limit the amount of waste water that isproduced by a food processing plant.

Additionally, the greater the amount of water used in commercialprocessing, the greater is the amount of heat energy that must beapplied to reach a desirable temperature level. If less water isutilized in a batch processing system, substantial savings in powerconsumption can be achieved. A batch processing system may, therefore,operate at a lower cost per pound of food processed.

Commercial rice cooking methods consume and excrete very large amountsof water. For example, in the commercial cooking of one cup of rice,prior methods required as much as a 20:1 ratio of water used to riceproduced pursuant to the processing method. A great advantage in foodprocessing would be a cooking method that allows food granules, such asrice, to be cooked with a ratio of water consumption to food productionof as little as 2:1 or perhaps even less.

Another problem in the food industry is the production of a uniformfinal product, especially in high production batch or continuousprocesses. For example, cooking cereal grains in a uniform manner sothat each grain receives substantially identical conditions duringcooking presents a challenge.

The challenge arises because numerous variables exist in processing andbecause of the difficulty in exposing each grain to the same overallhistory of cooking conditions. The first variable is the amount of heatapplied. The greater the amount of heat applied, the greater thegelatinization of starch within the grain, and the quicker the rice willcook. Furthermore, an increase in the pressure during the cooking ofrice will increase the rate at which the starch is gelatinized, andtherefore, it will speed the cooking of the rice. If the rate ofgelatinization of the rice is too high, or if the pressure andtemperature conditions are not optimum during the cooking and drying ofthe rice, the individual grains may be physically harmed by theformation of small pockets of air or dead space within the grain itself.These pockets cause the rice to become brittle after it is dried,resulting in an inferior product that consumers find undesirable.

Accordingly, what has been needed in the industry is a cooking apparatusand method that will provide for the uniform cooking of the foodgranules in a continuous processing system without using or excretingexcess water, and while avoiding the gluing together of the foodgranules.

SUMMARY OF THE INVENTION

The invention comprises a method of drying a food granule slurry whichcomprises water and wet food granules, wherein a wet food granule slurryto be dried is subject to a water separation step in which excess wateris taken from the wet food granule slurry. Warm air is then blown uponthe food granules to reduce the water content of the food granules, andthen they are agitated using rotary motion and dried while proceedingthrough a perforated rotating barrel. The barrel rotates at a speed thatresults in the application of no more than about 1 g of radial forceupon the food granules. Further, the invention provides separateidentifiable temperature zones along the path of the food granuleswhereby separately identifiable regions of the dryer are operated at airspeeds of greater than about 2000 feet per minute air outlet velocity.Further, sufficiently high temperatures are used to dry the foodgranules at a rate the produces dried food granules with desirabledensity characteristics in short rehydration times.

In another aspect of the invention, a method is provided wherein theresidence time of the food granules within the rotating barrel may beadjusted by allowing the food granules to remain within the rotatingbarrel until the food granules are sufficiently dried to facilitatetheir escape from the rotating barrel.

In another aspect of the invention, the step of separating excess waterfrom the wet food granules is accomplished by vibrating the food granuleslurry.

Further, a method is provided wherein the temperature and air velocitieswithin the rotating barrel are adjusted to facilitate the drying of thefood granules at a rate that is controlled as to both heat and airvelocity so as to avoid damaging the food granules during drying.

In another aspect of the invention, a method is provided wherein theflow of air along the path of the food granules is adjustably regulatedby dampening the flow to achieve optimum flow rates for a particularprocessing condition, a particular end product, or both.

Further, a method is shown wherein the residence time of the foodgranules is regulated using an adjustable hurdle near the exit of therotary dryer, wherein the adjustable hurdle facilitates the escape ofthe food granules after the food granules are sufficiently dry.

In another aspect of the invention, the method additionally comprisesthe step of providing the food granules to a bed dryer, wherein the beddryer comprises a conveyor for transporting the food granules throughthe bed dryer while blowing warm air upon the food granules.

In another aspect of the invention, the step of providing the foodgranules to a vertical dryer is shown, wherein the vertical dryer isadapted for reducing further the water content of the food granules.Additionally, a method is shown wherein the food granules comprise rice,and wherein the temperature zones provide for varying temperatures alongthe rotating barrel of the rotary dryer, further wherein the airvelocities within the rotating barrel are at least about 2700 feet perminute, wherein the variance in temperature provides a temperaturecontrolled drying process and an improved and more uniform rice product.

In another aspect of the invention, a method is shown wherein the foodgranules are transported within the rotating barrel from a proximal endof the rotating barrel to a distal end of the rotating barrel, furtherwherein the rotating barrel comprises an inner surface and an outersurface, the inner surface containing an advancement means adapted toadvance the food granules towards the distal end of the rotating barrelin the drying of the food granules.

In another method, the food granules are uniformly distributed withinthe rotating barrel during the drying of the food granules by mixing thefood granules with projections extending from a rotating shaft. Further,the food granules may comprise rice, wherein the air velocity in atleast one zone of the rotating barrel is greater than about 3000 feetper minute.

Additionally, a method is shown wherein a quicker rehydrating riceproduct is produced, the quicker rehydrating rice product being capableof being cooked by consumers within about 5 minutes or less.

In another aspect of the invention, a drying apparatus for reducing thewater content of a food granule slurry is provided comprising a rotarydryer, wherein said rotary dryer comprises an inlet port and an outletport and a body between the inlet port and outlet port. The rotary dryeris adapted for conveying a continuous stream of a wet food granuleslurry, wherein the wet food granule slurry proceeds into the inlet portand out of the outlet port. A rotating perforating barrel having aproximal end and a distal end is shown, wherein the rotating barrel islongitudinally positioned within the rotary dryer. Further, the proximalend of the rotating barrel is near the inlet port and the distal end isnear the outlet port of the rotary dryer, wherein the continuous streamof wet food granule slurry proceeds through the rotating barrel from theproximal end to the distal end of the barrel. Further, the food granulesare agitated and dried during advancement through the rotating barrel,said rotating barrel including an adjustable food granule escape meansproviding for escape of food granules from the rotating barrel after thefood granules are dry. Also, a blowing means is provided, wherein theblowing means provides warm air upon the wet food granule slurry duringits advancement along the body of the rotating barrel, the warm airevaporating water from the food granules, wherein the blowing meansprovides recirculation of warm air within the rotary dryer. A heatsource is also provided, wherein the heat source is adapted for heatingair which removes the water from the wet food granule slurry prior toits entry into the rotary dryer.

The apparatus above is also shown comprising a vibratory drainer,wherein the vibratory drainer is positioned adjacent the inlet port ofthe rotary dryer, the vibratory drainer vibrating the wet food granuleslurry to reduce the water content of the food granule slurry prior toits entry into the rotary dryer.

Further, an apparatus is shown wherein a rotating barrel is perforatedto facilitate high velocity flow of heated air from the blowing meansinto the rotating barrel among the food granules, in reducing the watercontent of the food granules.

The apparatus is also shown wherein dampers are provided to regulate theflow of air from the blowing means in a path through the perforations inthe rotating barrel.

Further, the apparatus is provided comprising a fan for providing aircurrents, the fan being mounted adjacent the rotating barrel of therotary dryer, wherein the fan provides a flow of air generally along thepath of the continuous stream of food granules, the fan providingassistance in advancing the food granules from the inlet port of therotary dryer towards the outlet port of the rotary dryer.

In another embodiment, the apparatus is provided wherein the blowingmeans provides air which is partitioned into separate temperature zonesalong the path of the food granules, wherein the temperature zones mayprovide for varying air temperatures to be applied to the continuousstream of food granules at different points along the path of the foodgranules from the inlet port towards the outlet port of the rotarydryer, further wherein the blowing means is adapted to provide an airvelocity within the rotating barrel of at least about 2700 feet perminute.

In another embodiment, the apparatus is shown wherein the rotatingbarrel is mounted within the body of the rotary dryer upon a shaft, theshaft running longitudinally from the inlet port to the outlet port, theshaft having a proximal end near the inlet port and a distal end nearthe outlet port, further wherein the g forces generated upon the foodgranules by rotation of the rotary shaft are no greater than about 1 gof force in a direction from the shaft towards the wall of the rotatingbarrel.

In another embodiment, the apparatus is provided wherein the rotatingbarrel additionally comprises an inner surface and an outer surface,wherein a portion of the inner surface comprises an advancement meansfor moving wet food granules from the proximal end of the rotatingbarrel towards the distal end of the rotating barrel.

Further, the apparatus is provided wherein the advancement meansadvances wet food granules using projections. Further, the rotary dryermay also comprise a mixing means within the rotating barrel, wherein themixing means acts to prevent the clumping of the wet food granule slurrywithin the rotating barrel. Further, the apparatus may include a mixingmeans which comprises a rotating column.

In another embodiment, the apparatus may include a rotating column whichadditional comprises fingers extending from the rotating column. Thedrying apparatus additionally may comprise a bed dryer, and perhaps avertical dryer.

The invention shown herein has numerous advantages, which include areduction in the amount of water that is used in the process, as aresult of efficient use of the water. In particular, water is used inquantities roughly equivalent to the amount of water that can beabsorbed by the food granules at that point in the process. Further, ahigh clarity of water at the end of the cooking process is disclosed,lending to the reuse of water. Water is drained from the vibratorydrainer just prior to the step of rotary drying, which allows the reuseof that water from that point in the process for other steps in theoverall process, resulting in proper presteaming and the reuse of properwater volumes and cooking temperatures.

Further, a significant advantage of this invention is the efficient,uniform and variable drying of the food granules as a result of thedesign of the rotary dryer. Temperature zones and air velocities areprovided which provide a superior product which cannot be obtained byuse of the apparatus and methods of the prior art. Further, an overallcoordinated process for processing food granules, and in particularrice, is presented. Additionally, the amount of waste water which wouldnormally be discharged after processing, or perhaps during drying, isreduced. Further, the energy consumption of the dryers of the presentinvention are reduced based upon the use of particular drying conditionsdisclosed herein, and upon the reduction in the water content of therice in the steps which occur prior to drying the rice. Further, theaccumulation of starch which adversely affects the overall process isminimized in this invention, facilitating the flow of food granulesthrough the system and through the dryer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the overall food processing system;

FIG. 2 is a flow chart showing the movement of the food granules amongthe various processing steps of the present invention;

FIG. 2A is a perspective view of the preferred embodiment of the steamcooker of the present invention;

FIG. 2B provides a cross-sectional view of the preferred steam cooker ofthe present invention;

FIG. 2C provides a detailed view of the shutters contained within thepreferred steam cooker of the present invention (the steam cookerdisclosed in FIGS. 2A and 2B);

FIG. 3 is a perspective view of a first alternate embodiment of thesteam cooker of the present invention;

FIG. 4 provides an exploded, detailed view of the interior of thealternate embodiment of the steam cooker shown in FIG. 3;

FIG. 5 discloses a cross-sectional view of the steam cooker shown inFIGS. 3 and 4;

FIG. 6 is a perspective view of another alternate embodiment of a steamcooker of the present invention;

FIG. 7 is a longitudinally exploded view of an alternative embodiment ofa steam cooker as shown in FIG. 6;

FIG. 8 is a closeup view of the arrangement of one of the cookingchambers within the steam cooker shown in FIGS. 6 and 7;

FIG. 9 is a perspective view of yet another embodiment of the steamcooker of the present invention;

FIG. 10 is a cross-sectional view of the steam cooker which wasdisclosed in perspective view in FIG. 9;

FIG. 11 is a cross-sectional view of the bottom portion of oneembodiment of a steam cooker in the present invention;

FIG. 12 is yet another embodiment of a steam cooker of the presentinvention;

FIG. 13 is a cross-sectional view of the steam cooker disclosed in FIG.12;

FIG. 14 is a perspective view of the rotary dryer of the presentinvention;

FIG. 15 is a cross-sectional view of the rotary dryer;

FIG. 15A is a cross-sectional view of the vibratory drainer which ismounted at the opening of the rotary dryer (as seen in FIG. 14) in thepreferred embodiment of this invention;

FIG. 15B is an end view of the vibratory drainer shown in FIG. 15A;

FIG. 16 is a detailed view of the barrel assembly housed within therotary dryer of the present invention;

FIG. 16A is a cross-sectional view of the rotary dryer of the presentinvention;

FIG. 16B is an end view of the barrel assembly, showing one arrangementof the containment mechanism that may be used in the invention;

FIG. 17 is a schematic view of the flow of food granules and waterthrough the processing steps of the present invention, including theflow of recirculated water.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The Overall Apparatus and Method

In the preferred embodiment of the present invention, food granules aretreated by prewashing, presteaming, steeping, and then transferring thefood granules to a steam cooker, followed by transfer to one or moredrying stages. After drying, the food granules may be packaged fordistribution to the consumer. Further, the present inventionadvantageously utilizes water in an economical manner by limiting thetotal amount of water used in the processing of the food granules, andby limiting the amount of water excreted in the processing of the foodgranules.

The amount of water used in the present invention of processing rice,for example, is usually the minimum amount of water needed to transmitrequired moisture and heat to each of the individual rice grains, and toprevent the formation of the excess free starch point, i.e., the "glue"point at which too much free starch is released, thereby causing therice to accumulate, and to no longer move through the processing steps.This is accomplished by adding water in quantities which are roughlyequivalent to the amount that the rice can absorb at each particularpoint in the process. Therefore, increases in pressure and temperaturewill allow for smaller amounts of water to be used in processing thecereal grains, while achieving a desired level of gelatinization of thecereal grains without release of excess free starch.

The overall processing system can be seen in FIG. 1. In FIG. 2, a flowdiagram depicts an overview of the typical flow of food granules throughthe processing steps of the present invention. All these steps will beexplained in greater detail below, flow diagram is provided as anoverview to the process. Food granules 58 are first subjected to aprewash step 59 in apparatus 12 illustrated in FIG. 1. After prewashing,food granules are provided to a presteaming step 60 (shown by referencenumeral 20 in FIG. 1), where they are presteamed in preparation forsteeping and water absorption step 61 which occurs within moving tanksor buckets 27 (as seen in FIG. 1). Of course, the buckets 27 seen inFIG. 1 are merely schematic, and actual implementation of the conveyorcontainers may adopt a different appearance from that shown in FIG. 1,while still performing the same function. After steeping, the foodgranules proceed into steam cooker 90, where they are cooked, and arethen provided along conveyor line 38 from the steam cooker to one ormore optional stations. As one option, a microwave or radiowave heater44 may be provided in-line, and a gas injection 42 may be provided tothe food granules. Further, an optional pneumatic conveyor heater 40 mayapply heat to the food granules.

Upon exiting the cooker and proceeding through conveyor line 38, thefood product is preferably entrained in a water slurry, which proceedsinto vibratory drainer 300 where water is drained from the slurry. Thefood granules then enter the rotary dryer 32, where the food granulesare dried in various temperature zones. Further, in an optional step thefood granules may be provided to a bed dryer 14, or a vertical dryer 15,or both, and the final product 54 (see FIG. 2) is dried and ready forpackaging.

Referring back to FIG. 1, food processing system 10 includes prewasher12 which receives the uncooked food granules, and performs a prewashingstep. Input 22 provides water to the prewasher 12 which is preferablyambient temperature at a temperature of approximately 25° C. If desired,the prewasher may be supplied with a hot or cold water input, not shownin FIG. 1. A hot water input might be used in cases where it is desiredto optimize free starch or surface starch removal. Prewashing may occurusing any of the standard methods of prewashing rice known in the art.The preferred method is the so-called "Jiff-Rice" system, disclosed inPatent Bulletin No. 51-22063 and in Japanese Patent No. 57/141257, whichare incorporated by reference.

In general, a Jiff-Rice unit prewashes rice by using a rotatingcentrifugal water application and separation method. Basically, the riceis washed in water, and the water is thrown off of the rice bycentrifugal force in the turning of a centrifugal drum within theprewasher. In the prewasher 12, rice typically is washed for about 10 to60 seconds. If the Jiff-rice process is not being employed, 10 secondsis the preferred time. If the Jiff-Rice system is employed, then thewashing time may be as much as 60 seconds or perhaps even more. Thisprewashing is known in the art pursuant to the above-described patents,and perhaps other patents.

The prewashing serves to provide some moisture to the rice, withoutgiving it too much moisture in the early stages of the process. If riceor other uncooked food granules are given too much water early in theprocess, undesirable gluing effects will be observed, slowing thetransport of the food granules through the cooking apparatus.

After the relatively brief prewashing step, food granules are depositedupon conveyor 16 for transport into the presteamer unit 20, which issupplied with steam from steam line 49. The presteamer is preferably abed conveyor-type steam unit, of the type known in the art which sprayssteam onto the bed of food granules as they pass through the steamerfrom above the conveyor down onto the conveyor, and also from below theconveyor onto the food granules. The presteaming step is important tothe overall invention because the food product is exposed to arelatively brief amount of heat and moisture, in order to avoid damagingor mobilizing surface starch in the early stages of cooking of the foodgranule. In the preferred method, each individual granule of rice willbe subjected to the presteamer operation for approximately 5 to 30minutes. Of course, this may be modified as desired, and presteamingtime will depend upon the variety of the product being produced.

The presteaming step assists food granules, and in particular, assistscereal grains such as rice in absorbing a relatively small, butappropriate, amount of water at this point in the process. This step,therefore, prepares the rice granules to be in a condition for absorbingfurther quantities of water in appropriate amounts in subsequent steps.In the process of the present invention, one of the most importantfactors is that the cereal grains are presteamed before they are steepedin the buckets 27 in route to the steam cooker. This process facilitatesa controlled moisture input into the food granules or cereal grains thatincreases the ability of the food particle to be cooked without showingundesirable gluing effects. In particular, the water which istransported along with the cereal grains during cooking is less likelyto contain large amounts of loose starch which has been extruded fromthe cereal grains where a presteaming and a short steeping step areprovided, as in the present invention, before steam cooking the rice.

After the food granules pass through the presteamer unit 20, they aredeposited into buckets 27 which are intermittently advanced uponconveyor line 50. The prepared conveyor/bucket system is of acommercially available design from Nippanki Industrial Co., Ltd. ofJapan. Preferably, approximately 50 pounds of food granules aredeposited into each bucket along conveyor line 50. Sensing mechanisms(not shown) detect when the bucket receives a full load of foodgranules, and at that point the conveyor system advances one station toa point at which the dispenser line mixture 34 dispenses water into thebucket 27, for a steeping step.

The dispenser line mixture 34 may be comprised of fresh hot water whichcomes from hot water line 18, or may be comprised of recirculated waterfrom recirculated water line 30. Depending upon the type of foodgranules processed, and the processing conditions required, it may bepossible to provide recirculated, or recycle water, from recirculatedwater line 30, which has already been processed, back into buckets 27for reabsorption by food granules, thereby minimizing the amount ofwater used in the overall processing system, and reducing the amount ofwaste water in the overall processing of the food granules.

The amount of water introduced into each bucket 27 is typically theamount of water needed to provide a ratio of about 1:1 between theamount of food granules introduced into the bucket, and the amount ofwater introduced into the bucket, on a weight basis. In particular, theamount of water introduced is regulated such that it may be completelyabsorbed, or nearly completely absorbed, by the food granules beforethey are deposited into the steam cooker 90.

The steeping water provided into buckets 27 is preferably about 80° C.,although the water temperature will vary for different processingconditions and different food granules. Further, in the processing ofrice, different varieties of rice may require a different watertemperature for steeping. Each 50 pound charge of food granules which isdeposited into bucket 27, and then supplied with water, then proceeds instepwise fashion towards the steam cooker 90. Preferably the rice willremain in its associated bucket and hot water for approximately 5-30minutes (depending upon processing conditions and variety of foodproduct). The preferred time for milled white rice is about 10 minutesfor appropriate steeping and absorption of the water into the ricegranules. Upon reaching the steam cooker, the contents in each bucketare emptied into the steam cooker, and each bucket is returned back tothe deposit station along the undercarriage of the conveyor line 50. Abucket cleaning station may be included if needed.

After proceeding through the steam cooker 90, which will be described inmore detail in the description that follows, the cooked rice and waterslurry emerges along conveyor line 38, where it advances to a vibratorydrainer 300, and then to a rotary dryer 32. However, one or moreoptional steps may occur between the steam cooker and the rotary dryer,including the application of microwaves, radiowaves, or otherelectromagnetic radiation to the food granules at microwave heater 44.As another option, the food granules may be subjected to a gaseoussubstance, such as carbon dioxide at gas injection station 42. Asanother option, depending upon the type of food granules processed, apneumatic conveyor heater 40 may be provided to flash off excess waterprior to entry of the food granules into the rotary dryer 32.

Further, chemical treatments of the rice may be desirable in some cases.The food granules may be conditioned by the addition of lecithin, riceoil, sugar, phosphoric acid, adipic acid or other acids. In theprocessing of rice, for example, such chemical additives are useful inimproving the quality of the final product.

It should be noted that the gas injection and the microwave heating mayserve several functions, including drying the surface of the foodparticles to facilitate the entry of water into the particle, therebysoftening the food granule. In the case of rice, for example, microwaveheating of the grain produces small fissures in the exterior of thegrain, allowing for moisture entrapment within the grain during cooking,providing a highly desirable rice product. Carbon dioxide gas may beprovided to cereal grains in order to improve the texture and to aidgelatinization of the starch within the grain for a more consistentcereal grain product that is more evenly cooked and more desirable toconsumers. Due to the nature of the functions provided by these steps,they might be performed, either individually or in combination, or atother additional or different points in the overall process.

Upon arriving at rotary dryer 32, the food product is exposed to hot airin a manner to be described in greater detail below. An alternate typedryer might also utilize sonic energy to aid drying. The food granulesproceed through the rotary dryer, and optionally may proceed into a beddryer 14. Whether or not a bed dryer is required will depend upon thetype of food granule processed, and the degree of drying desired. Afterdrying in the bed dryer, food granules may optionally proceed to avertical dryer 15. Vertical dryer 15 is adapted for reducing themoisture content of food granules to a greatly reduced level. Both thebed dryer and vertical dryer are of conventional design.

Various aspects of the overall process will now be examined in greaterdetail.

The Preferred Embodiment of the Steam Cooker

Steam cooker 90, the preferred embodiment for steam cooking in thepresent invention, is shown in FIG. 2A. The food granules, which haveabsorbed water just prior to entry into the steam cooker, proceed alongconveyor line 50 as seen at the top of FIG. 2A. The food granules, withabsorbed water, are deposited from bucket 27 into the top portion of thesteam cooker 90. Further, hot water line 18 provides hot water to hotwater line 99 to the lower section of the steam cooker 90, and thiswater may be used to flush the food granule slurry out of the steamcooker, and to provide an aqueous medium of transport of the slurry tothe rotary dryer. (See FIGS. 3-5).

Flow direction arrow 95 shows the direction of flow of the uncooked foodgranules into the steam cooker. A hot water line 18 provides hot waterfor cleaning jet nozzles 91 which are located in the top portion of thesteam cooker 90. The food granules are deposited onto drain screen 93,where they are vibrated, and moisture is allowed to drain from the foodgranules prior to their passage through steam chamber aperture 312 seenat the top and center portion of FIG. 2A. The circular retention bowl 92receives the food granules, and directs them downward into the steamchamber aperture 312 with the vibrational action of the drain screen 93.

The food granules proceed through steam chamber aperture 312 into thelower portion of the steamer as seen in FIG. 2A. A plurality of steamlines, for example steam line 318 and 310, are seen entering the steamerwall 306, where they provide steam to the food granules on the interiorof the steamer 90. Rotating shutters 308 are seen in cut-away view andin phantom lines at the middle and lower portion of FIG. 2A. Therotating shutters 308 are rectangular in shape, and extend between theside walls of the steamer, and contain steam ports 320 upon their uppersurface. Food granules proceed through the various stages, or layers, ofrotating shutters in stepwise fashion, where they eventually arereleased into hopper 314, seen at the lower portion of FIG. 2A. Thehopper is typically a water filled bath which cools the food granules,and provides a slurry medium in which food granules proceed prior toadvancement through exit chute 316 out of the steam cooker 90. Waterlines, gas lines or vacuum lines may be provided in the region of theexit chute 316 to facilitate the discharge of food products from thecooker. Such equipment is more fully discussed in connection with theembodiment of FIGS. 3-5, but could preferably be employed in thisembodiment as well.

FIG. 2B shows a cross-section of the lower portion of the steam cookerpreviously described in FIG. 2A. At the top of FIG. 2B, the steamer wall306 is seen on either side of the figure, with four vertically spacedlayers, or rows, of rotating shutters 308 extending laterally betweensteamer walls 306. FIG. 2B shows the preferred embodiment of theinvention, that is, a series of rotating shutters 308 to advance thefood granules from one stage to the next in sequence. Further, it may beseen that the lower portion of the cooking apparatus seen in FIG. 2B issomewhat wider than the upper portion, allowing for greater throughputof the food granules, with maximum cooking effectiveness and minimumadverse "gluing" effects, and also to allow for swelling of the foodproduct, such as rice, due to the absorption of water. Perforated steamlines 324 are seen in cross-section in FIG. 2B, where they proceedlaterally beneath rotating shutters 308. The perforated steam linesserve two functions. First, they provide steam for the cooking of thefood granules. Second, they provides axes or hinges of rotation for therotating shutters 308. Shutter gap space 338 is the operating gapbetween rotating shutters 308, and it facilitates free rotation of theshutters, while still retaining food granules within each layer of thesteam cooker. FIG. 2C, which is discussed in more detail below, showsthe rotated position of the shutter 309 seen in phantom lines in FIG.2C. Each of the shutters seen in FIG. 2B functions by rotating as shownin FIG. 2C.

Perforated steam lines 322 and 324 in FIG. 2B provide steam to cook foodgranules. Further, steam jet 326 extends downwardly and somewhatlaterally from the perforated steam lines, and steam ports 320 areevident on the top side or upper side of each rotating shutter 308, toprovide steam upward into the food granules. In this way, each charge offood granules is steamed from above and below as it proceeds in stepwisefashion through the steam cooker.

FIG. 2C shows a closeup view of one rotating shutter 308 and itsassociated perforated steam line 322. In particular, it may be seen thatsteam ports 320 exist upon the upper side of the rotating shutter 308,and steam is allowed to exit these ports. Steam conduit 334 carriessteam through the center of the perforated steam line 322. Outer steamline wall 336 serves as a pivot point, or hinge, upon which the rotatingshutter 308 may turn on its axis approximately 90°. The rotated positionof the shutter 309 is seen in the phantom lines extending from the topto the bottom of FIG. 2C. Steam conduit 334 carries the steam from theexterior of the steam cooker to the steam jet nozzle 322 and the steamports 320. Steam jet 326 is seen as it exits from the steam jet nozzle332. The axis of rotation of rotating shutter 308 is shown by arrows ataxis 328 and axis 330.

In the operation of the steamer seen at FIGS. 2A-2C, rice falls throughaperture 312 and comes to rest on top of the uppermost row of closedshutters 308. While in this position, steam is provided to the rice foran appropriate duration of time from steam ports 320 and 322. Theshutters will then be rotated to cause the rice to fall and be collectedon the immediately adjacent vertically spaced row of closed shutters,where the rice will be subjected to further steam and cooking. The ricewill then proceed through the cooker onto each immediately adjacent rowof shutters for being subjected to further steam, until the rice hasachieved the appropriate degree of cooking and moisture absorption.

The preferred operation is to rotate the rotating shutters by externalactivation approximately once per minute to minute and a half in thecase of white rice. Other types of rice would use other processingconditions, and might require a longer or shorter period of time betweenactuation of the rotating shutters. Once actuated, the rotating shutterswould rotate from a few degrees to as much as 90°, as necessary tofacilitate the movement of the food granules from one stage (zone) downto the next zone. In actual practice, the steamer preferably would haveapproximately 10 zones, upon which food granules would proceed instepwise fashion through rotating shutters. For illustrative purposes,only approximately four or five zones are shown in FIGS. 2A-2C.Different types of food granules and different varieties of rice mightrequire a different number of zones, and as few as two or three zones,or less, might be required for certain applications, while as many as 30zones might be desirable in other applications.

The actuating method for the rotating shutters may be accomplished byusing a motor, hydraulic equipment, or perhaps pneumatic air equipment.The total residence time of rice in the steamer is approximately 5 to 30minutes, in the case of long grain white rice. It is less or more forother varieties of rice, and for other varieties of food granules. Theresidence time for short grain rice (i.e., faster hydrating rices) islikely to be less, while the residence time for slower hydrating rices,such as parboiled and brown, and wild rice is likely to be greater. Inthe case of long grain white rice, the weight of rice to be held by eachrotating shutter in each stage (preferably) is approximately 2.8kilograms. Further, the thickness of the rice layer, in the case of longgrain white rice, would preferably be approximately five centimeters. Inorder to secure the dropping of rice by turning the rotating shutters,the thickness of the rice upon the top of each rotating shutter wouldpreferably be smaller than the rotating radius of the rotating shutter308, to facilitate the movement of rice from one zone down to the nextzone. In some applications, it may be desirable to feed rice or foodgranules out of the steam cooker and directly into a rotary dryer.However, in the preferred embodiment, and as seen in FIG. 1, it isbelieved that pumping the rice from the steam cooker in the form of aslurry, into a vibratory drainer 300, and then into the rotary dryer isthe most efficient method for the processing of rice. The processing offood granules, and different varieties of rice, may occur by differentmethods.

In the preferred operation, the pressure within the cooker will be keptbelow 15 psi in order to avoid high pressure regulations which areimposed upon such high pressure vessels. As the rice exits the cooker,its water content will be approximately 50%-65% water. These generalconditions will apply not only to this preferred embodiment, but alsothe other embodiments of cookers as well.

Alternative Embodiments of the Steam Cooker Using a Central RotatingMechanism

FIG. 3 shows an alternate embodiment for the steam cooker of the presentinvention. In FIG. 3, steam cooker 87 is shown, and the food granules,which have absorbed water just prior to entry into the steam cooker,proceed along conveyor line 50 as seen at the top of FIG. 3. In thisalternate embodiment, the food granules, with absorbed water, are dumpedfrom bucket 27 into the top portion of the steam cooker 87. Flowdirection arrow 95 again shows the direction of flow of the uncookedfood granules into the steam cooker. A hot water line 18 provides hotwater for cleaning jet nozzles 91 which are located in the top portionof the steam cooker 87, and also provides hot water to hot water line99. The food granules are deposited onto drain screen 93, where they arevibrated, and moisture is allowed to drain from the food granules priorto their passage through food granule inlet 94, which is seen at the topand center portion of FIG. 3. The large circular retention bowl 92receives the food granules, and it directs them downward into the foodgranule inlet 94 with the vibrational action of the drain screen 93.

Different processing conditions and different types of food granuleswill determine what type of steam cooker is most desirable for eachapplication. For example, the preferred embodiment of the presentinvention is the steam cooker shown in FIGS. 2A-2C, and it is preferredfor long grain white rice. Nevertheless, short grain rice or othervarieties of rice, such as parboiled rice, may be more advantageouslycooked using the rotating mechanism of the steam cooker shown in FIGS.3-5, or perhaps in the alternate embodiments seen in FIGS. 6-12. Each ofthe steam cookers shown in this specification is contemplated as part ofthis invention, and different varieties of food granules will preferablyuse different variations of the steam cooker.

Food granules are deposited into the housing 89 which contains thepropeller assembly 97 (the cylindrical dotted portion seen at the centerof FIG. 3). The propeller assembly 97 comprises several parts, whichwill be seen in the exploded and detailed view of FIG. 4.

Steam lines 49 provide steam to the exterior wall of housing 89 as seenin FIG. 3. Further, rotary blades 98 are seen in phantom lines at thecenter of FIG. 3, as part of the propeller assembly 97. Hot water line99 provides hot water to the hopper 80, which may be used to flush thefood granule slurry from the hopper, and to provide a water transportmeans to the rotary dryer. Recirculated water line 30 also extends intothe housing 89.

At the lower portion of FIG. 3, steam line 49 is seen entering thehousing, and hot water line 96 provides hot water to the lower portionof the steam cooker comprising the hopper 80. At the lower portion ofFIG. 3, in phantom, can be seen the rotating crank shaft 103. Therotating crank shaft 103 is connected to the propeller assembly 97, andit rotates, causing the rotation of the rotary blades 98.

During operation of the steam cooker, the rotary blades 98 act to propelthe food granules from the top of the cooker down to the bottom of thecooker. The blades also support the food granules, and provide a uniformmixture of food granules while the granules are being steamed in thesteam cooker. Further, the rotating action provided by rotating crankshaft 103 assists in preventing the gluing and sticking together of thefood granules, which may otherwise occur.

Support frame 112 supports the steam cooker, and power is provided tothe rotating crank shaft 103 by way of motor 102, which is connected toa belt 100 wrapped around a pulley 101.

In FIG. 4, an exploded and detailed view of the propeller assembly 97 isprovided. The central axis 109 of the propeller assembly is seen asdotted lines. FIG. 4 also shows a rotating scraper cap 105 upon which ismounted an optional scraper connecting unit 107, only part of which isshown in FIG. 3. The scraper connecting unit 107 is connected to twoseparate scraper arms 106, which in turn are connected to scrapers 104.The rotating scraper cap 105 is fixedly connected to the rotating crankshaft 103 which extends up through the entire assembly as shown in FIG.4. The scrapers rotate to effect a uniform distribution of the foodgranules as they enter the interior of the steam cooker 90.

At the center and left portion of FIG. 4, the housing 89 is seen incut-away view whereby the stationary blades 108 may be seen on theinterior wall of the housing 89. Twelve stationary blades are shown onthe cut-away section, which comprises approximately one-half of theentire housing 89. Steam chamber 110 may be seen on the exteriorperiphery, and it is within the steam chamber 110 that steam is injectedby way of steam lines 49 and then distributed inward through porous wall123. Porous wall 123 may be formed, for example, by a cylindricallyshaped portion of steel or aluminum mesh.

Further, in FIG. 4, the rotating cylinder 111, which is connected to therotating crank shaft 103 is seen at the top right portion of FIG. 4. Itrotates within the housing 89, and comprises a plurality of rotaryblades 98 which are arranged in three distinct zones along thelongitudinal length of the rotating cylinder 111. The rotary blades 98assist in advancing the food granules through the cooking apparatus, andalso provide a platform upon which the food granule slurry may rest, toprevent the pressure of the slurry from becoming so great that largeglobules are formed within the chamber. Thus, rotary blades 98 andstationary blades 108 help to keep the food granule slurry bothsupported and mixed, to prevent globular portions from forming withinthe steam cooker 90.

The rotating cylinder 111 is mounted upon the rotating crank shaft 103which extends along the central axis 109 up through the rotatingcylinder 111 where it engages the rotating scraper cap 105.

Mist line 114 extends up through the interior of the rotating crankshaft 103 to provide a mixture of steam and water mist to the foodgranule slurry. Further, steam line 49 is provided with a plurality ofsteam nozzles 113 which are located along the interior of rotatingcylinder 111, and provide jets of steam from the interior through thewall of the rotating cylinder 111 and out into the chamber where thefood granules are contained. Like exterior wall 123, rotating cylinder111 is porous to permit the passage of steam. Thus, the food granulesreceive steam from two directions, from steam chamber 110 from theoutside, and from the inside by way of steam nozzles 113, in order toachieve more uniform cooking and water absorption.

At the lower right portion of FIG. 4, one can see housing 89 which isshown in a cut-away view, and hot water line 99 extends out from thehousing. Recirculated water line 30 drains excess water from theinterior of the steam chamber and, as seen in FIG. 1, providesrecirculated water for reabsorption along dispenser line mixture 34 backinto buckets 27. In this way, less water is utilized in cooking, andmore water is retained within the processing system.

Spoke 115 provides a structural member supporting the steam cooker, anda hopper 80 essentially comprises a water bath near the lower portion ofthe steam cooker upon which the rice falls after it is cooked. Steamline 49 enters the steam chamber through the wall of hopper 80. Hotwater line 99 also provides hot water, if needed, to the hopper 80. Insome cases, a hot water flush may be desirable to flush globules of foodgranules out of the hopper 80, and into conveyor line 38 for transfer tothe rotary dryer 32. Power is provided to the rotating crank shaft 10 byway of motor 102, which is connected to belt 100, wrapped around pulley101.

FIG. 5 depicts a cross-section of the steam cooker shown in FIGS. 3 and4. At the top of FIG. 5, uncooked food granules 62 are dumped into theretention bowl 92, where they are vibrated upon drain screen 93. Hotwater line 18 is seen at the top of the retention bowl 92, where itprovides a plurality of cleaning jet nozzles 91 that may be used toclean the screen or to provide a hot water spray upon the food granulesif desired.

Vibration of the drain screen 93 is provided by vibratory motor 117,which provides vibrating action for the entire drain screen. Water isdrained into drain space 118 around the periphery of the food granuleinlet 94, and the water is collected and drained away through streamerdrain line 37. As seen in FIG. 1, the contents of steamer drain line 37is later filtered, and some portion of that water may be reused andreabsorbed along the dispenser line mixture 34 into bucket 27 (see FIG.1). Also, some portion of this recirculated water may be drained atdrain 29 as seen in FIG. 1.

FIG. 5 illustrates the manner in which the food granules proceed throughthe food granule inlet 94 as indicated by the arrow at the top. Thegranules are dispersed, and fall upon the rotary scraper cap 105,wherein scrapers 104 rotate in distributing the food granules, andhelping to feed them into the steam cooker. Scraper connecting unit 107is seen as it forms its connection between rotating scraper cap 105 andscrapers 104.

The food granules then proceed into the steam cooker in a continuousbatch, and they are mixed and distributed with the assistance ofstationary blades 108, which do not move, and rotary blades 98, whichare rotated in three discrete zones as seen in FIG. 5, around theperiphery of the rotating cylinder 111. The rotary blades contain ontheir underside a steam line 122, from which steam nozzles 124 providesteam to the food granules within the chamber. These steam lines 122receive steam from water mist line 14.

Rotating crank shaft 103 rotates the rotating blades 98 at a relativelylow rate of speed, in the range of 1 rpm to 10 rpm and preferably about5 rpm. Care should be taken not to agitate the granules to anysignificant degree, so as to avoid breakage of the individual kernels.As a result, the rice proceeds through the cooking chamber, beingsteamed from the exterior by a plurality of steam jets around thecircumference of the cooker, which are contained within steam chamber110. Steam lines 49 are seen as they enter from the exterior of thesteam cooker into the interior space of steam chamber 110.

Hot water line 99 is seen on the right side of FIG. 5, and level sensor116 is slightly below hot water line 99. Below that can be seenrecirculated water line 30, which may drain off excess water from thehopper 80 and provide it to be recirculated and perhaps reabsorbed inbuckets 27 as seen in FIG. 1. Sensor 125 is seen below recirculatedwater line 30, and it operates to sense the temperature of the water toprevent the water temperature from becoming too great. This sensor mayassist in minimizing starch damage and gluing effects.

As shown in FIG. 5, hopper 80 is seen as the portion of the steam cookerwherein the rice falls after it is thoroughly mixed and cooked. Steamline 49 is seen at the lower left portion of FIG. 5, and hot water line96 is provided in the region of the hopper 80 to facilitate a hot waterflush, if desired.

Motor 102 provides power generated by way of belt 100, which drivespulley 101, thus turning the rotating crank shaft 103. Steam line 49 andhot water line 18 are seen at the very bottom of FIG. 5, where theyenter the region of the crank shaft 103 and proceed upward as seen inthe dotted phantom lines along the interior of the crank shaft 103. Mistline 114, which provides a steam and water mist to the food granuleswithin the chamber, may be adjusted to provide the desired mixture ofwater and steam which is necessary for cooking the particular variety offood granule. Some food granules may require more water and less steam,while others require more steam and less water to fully cook thegranules prior to exit from the steam chamber.

In the preferred operation, rice will remain within the cooker 90 forapproximately 10 to 15 minutes, approximately the same amount ofresidence time as in the steeping operation. Thus, the steeping andcooking operations may be coordinated. While the rice is in the cooker,it will continue to absorb water in an optimal manner, i.e., in anamount roughly equivalent to the amount of water that can be absorbed bythe granules at that point in the process, and the starches aregelatinized. The temperature and pressure within the cooker will becoordinated to achieve optimal results for cooking the rice whileavoiding undesirable "gluing" or sticking.

Further Alternate Embodiments of the Steam Cooker

In general, it should be noted that numerous embodiments of steamcookers may be used in the present invention. Different arrangements ofthe cooker will be preferred for different types of food granules, anddifferent varieties of cereal grains or different varieties of rice mayrequire variations in the design of the steam cooker to maximize cookingeffectiveness.

FIGS. 6-8 illustrate an alternate embodiment of the present invention,which also may provide advantageous results for steaming certain typesof food granules such as certain varieties of rice. Bucket 27 is seen atthe top of FIG. 6 where it proceeds along conveyor line 50, dumping aload of uncooked food granules 62 into the top portion of the steamcooker.

The granules are deposited into a funnel segment 64 at the upper end ofthe steam cooker. The uncooked food granules 62 preferably willfree-fall upon cone spreader 78 where the food granules are distributedin an even fashion around the periphery of cone spreader 78. Further,funnel segment 64 may be selectively rotated to assist in the evendistribution of food granules around its periphery, thus assisting inthe uniform and complete cooking of food granules. The rotation could beclockwise or counter-clockwise, and in the preferred embodiment, therotation of the funnel segment 64 would be in the same direction (i.e.,clockwise or counter-clockwise) as the rotation of the discharge segment68.

In the steam cooker 46, cylindrical housing 74 is comprised of aplurality of segments, including funnel segment 64, middle segment 66,and discharge segment 68. Pipe entry segment 148 is located between themiddle segment 66 and the discharge segment 68 in the preferredembodiment as seen in FIG. 6. Through segment 148, hot water line 18 andsteam line 49 enter the cylindrical housing 74, as seen in FIG. 6. Thefood granules proceed through the segments, and they are picked up bythe rotating discharge segment 68 as it turns on its central axis. Thefood granules proceed into hopper 80, and then fall into venturi segment84.

The flow rate of food granules through the steam cooker may beinhibited, especially near the discharge end of the steam cooker athopper 80. To encourage free flow of food granules through the hopper,and especially in the case of cereal grains or rice products, which mayexhibit a gluing effect which prohibits advancement of the rice grainsthrough the steam cooker, the venturi segment 84 may be provided with anair or gas feed line 82 (which could alternatively provide a vacuum)that provides air or gas pressure (or a vacuum) to assist in theadvancement of the food granules from the butterfly valve 86 to exit thesteam cooker through butterfly valve 88.

The rotation of various segments of the cylindrical housing in thealternate embodiment, as seen in FIGS. 6 and 7, provides for greateruniformity of cooking and distribution of food granule flow through thesteam cooker. In the case of cereal grains, once the cereal grains passinto the steam cooker, the goal is to cook the grains at the lowestpossible moisture content to reduce the amount of time required in thesteam cooker. A reduction in the moisture level and the time requiredfor cooking is advantageous, but the reduction in moisture level mustnot be so great as to cause undesirable gluing effects within the cavityof the steam chamber. This principle applies not only to thisembodiment, but to all in this disclosure.

Typically, only a small amount of pressure is achieved within the steamchamber of FIGS. 6-12, as in the preferred embodiment shown in FIGS.2A-2C, and the alternate embodiment seen in FIGS. 3-5; the pressure ispreferably maintained below 15 psi to avoid the necessity for complyingwith governmental regulations and local codes for pressurized vessels.This, of course, is only preferable and may be modified as desired orneeded. The pressure is maintained by the downward force of the ricewithin the vessel and by the introduction of steam under pressure intocooking chambers.

A small opening 75 at the top of conical section 78, as seen in FIG. 6,permits steam to escape from within the cooking vessel, but the openingis sized to restrict the escape of steam in order to achieve the desiredinterior pressure.

The vessel is typically operated at a pressure of approximately 5 psi,but this may be varied as desired. A greater pressure within the steamchamber will increase the temperature of the chamber, without acorresponding addition of moisture. Thus, the primary variables in thecooking of food granules are the pressure, the temperature, and themoisture content of the food granule slurry.

In the embodiment shown in FIG. 6, there is synchronized rotationbetween the discharge segment 68 and the funnel segment 64. Hot water isprovided through hot water line 18 at a temperature of between 90° C.and 100° C. It is preferred that the cooker be arranged vertically, sothat the flow of food granules through the cooker is assisted bygravity. The average time a particular food granule resides in the steamcooker itself is preferably about 10 to 15 minutes, although cookingtimes will vary widely for different types of food granules. Asynchronized rotation between segments 64 and 68 of about 5 revolutionsper minute is the maximum typically used; the minimum rpm of therotating segments is 0.2 rpm.

In FIG. 7, an exploded view of the cooker of FIG. 6 is shown. Steam jet76 emerges from the top of cone spreader 78 in the funnel segment 64.Funnel segment 64 rotates, preferably in synchronous rotation withdischarge segment 68. Along the central axis of the steam cooker iscentral hot water line 138 and central steam line 140. These linesprovide hot water and steam to the cooking chambers 142 which arearranged around the periphery of middle segment 66.

The cooking chambers are preferably separated by partitions 143,although it is not required that the chambers be separated in such away. Pipe entry segment 148 is located between middle segment 66 anddischarge segment 68, and it provides for entry of the hot water line 18and steam line 49 from the exterior of the steam cooker into the plenumchamber 144, which is the chamber running along the center of the steamcooker from which steam and hot water emanates into the cooking chambersradially outwardly. Discharge segment 68 is provided with a spreaderwindow 154 which, when the discharge segment 68 is rotated, provides auniform distribution and spreads the food granules in an even manner asthey emerge from the various cooking chambers 142.

Spreading of the food granules in this way provides for more uniformcooking, and a more advantageous distribution as the food granule slurryproceeds through the processing of the present invention. Hopper 80collects food granules and they are discharged through venturi segment84, which comprises butterfly valve 86 and butterfly valve 88. Air orgas may be provided along air or gas feed line 82, and a vacuum may bepulled to provide a venturi effect which may advance food granules outof the steam chamber more efficiently.

In FIG. 8, a pie-shaped section of a cooking chamber 142 is seen inexpanded view, which shows two partitions 143, the exterior wall 146 andthe perforations 152 on the interior perforated wall 150. Hot waterand/or steam may be provided through perforations 152 to the foodgranules residing in cooking chamber 142. Additionally, openings may beprovided in the exterior wall 146 to receive hot water and/or steam froma supply plenum (not shown). In this manner, steam is provided from twodifferent directions in order to provide more uniform cooking and tobetter regulate the water supply and absorption.

In operation of the embodiment shown in FIG. 7, rice is conveyed inbuckets 27 by way of conveyor 50 to the funnel segment 64, where it isdeposited into the funnel segment. Food granules will accumulate in eachchamber and will be subjected to an internal pressure of 5-15 psi. Atypical residence time of the food granules within a chamber will beapproximately 10 to 15 minutes, although this can be varied as desired.Most preferably, steam will be supplied both from the openings 152 (FIG.8) and from openings in the exterior wall 146, in order to achieve asmuch uniformity in the exposure of each individual grain as ispractical.

As indicated above, food granules will accumulate in each cookingchamber by virtue of discharge segment 68. As will be appreciated,opening 154 in segment 68 permits only a limited amount of food granulesto drop by gravity from each cooking chamber. Surface 155 provides asupport surface on which the cooked food granules rest, until opening154 passes each chamber in turn to permit a limited quantity of rice todrop.

In FIG. 9, still another alternate embodiment of the steam cooker isdisclosed. Food granules are provided into input funnel 172 where theyfall into entry chamber 174 and upon the surface of cone spreader 78. Inthis embodiment, the steaming chambers are provided in an alternatingarrangement, such that cooking chambers 142 alternate with plenumchambers 144 around the periphery of a central chamber 184. Steam isprovided through steam line 72 from the exterior of the steam cooker andit proceeds into the four plenum chambers where it is provided throughwire mesh or perforated walls into the respective cooking chambers 142.

Further, an arrangement whereby a spindle 182 is aligned along thecentral axis of the steam cooker is seen in FIG. 9. A discharge paddle180 rotates discharge paddle blades 176 to assist in the even spreadingof food granules and discharge of food granules from the bottom of thesteam cooker. In this way, food granules may be evenly distributed anddischarged through hopper 80 and through discharge port 178.

FIG. 10 shows a cross-sectional view of the steam cooker shown in FIG.9, whereby the steam enters through steam line 72 and is provided tocooking chambers 142 by way of perforated walls which extend generallyradially and define the cooking chamber.

FIG. 11 shows an alternate apparatus and method which may be utilized toassist in the advancement of food granules out of the bottom of thecooking chamber. In FIG. 11, cooking chamber 142 is shown wherebyrotating distributor 188 rotates about the central axis of the cookingchamber to allow cooked food granules 190 to be evenly distributed andin their exit from the cooking chamber. Rotating axle 194 is seen on theright side of FIG. 11. Food granules proceed in a downward progression.Upper frame support 192, lower frame support 198, and frame support 196provide the exterior surface of the cooking chamber. The housing floor200 provides stability to the bottom of the cooking chamber.

In another embodiment of the steam cooker of the present invention, asseen in FIG. 12, steam may be provided through steam line 206 intorotary valve 204 and ultimately into central chamber 184 (seecross-sectional view in FIG. 13). In this arrangement, the cookingchamber is substantially the same as that of FIG. 9, with the exceptionthat steam is provided directly from steam line 72 into the centralchamber 184, where it is distributed into cooking chamber 142 along thecentral axis outward from the center of the chamber. In other respects,the embodiment shown in FIGS. 12 and 13 is substantially similar to thatshown in FIGS. 9 and 10.

The preferred dimensions of the steam cooker of the present inventionwould be with an outer dimension (measured across the cooker) ofapproximately 8 feet, although other sizes could be utilized.

The Drying Apparatus and Methods

A rotary dryer is used in the preferred embodiment of this invention fordrying the food granules. In some cases, for certain types of foodgranules, a bed dryer may also be used. In the drying of rice, forexample, a rotary dryer and a bed dryer typically are used. Further, inmaking a highly dehydrated rice such as a quick rehydrating variety ofrice, a vertical dryer also is used to reduce the moisture content ofthe rice to a low level.

Further, a vibratory drainer, seen in FIG. 1, is preferably used incases where the food granule slurry is pumped in a water slurry formfrom the steam cooker to the rotary dryer. FIGS. 15A and 15B shown,respectively, a cross-section and an end view of the vibratory drainer,as shown affixed to the entrance of the rotary dryer in FIG. 1.

Of course there are numerous methods of transporting the food granulesfrom the steam cooker to the rotary drying apparatus, and transport byusing a water slurry is only one method. For example, a dry transportmethod could use a combination of rice/air transport by blowing the ricethrough a conduit, or rice could be transferred on a conveyor belt, ifsufficient apparatus (such a breakers) are employed to prevent lumpingof the food granules.

The primary purpose of the vibratory drainer as seen in FIGS. 15A and15B is to take water out of the rice early in the drying process, and toreduce the moisture content of the rice so that the energy consumptionof the dryer will be reduced. Further, the amount of maintenancerequired with regard to the drying apparatus may be reduced by avoidingentry of large amounts of water into the dryer. Further, reducing waterfrom the food granule slurry in the vibratory drainer helps to create amore uniform feedstock to the dryer.

FIGS. 15A and 15B show the details of the vibratory drainer 300. Thedrainer preferably receives the input food granule slurry 344 as seen inthe top of FIG. 15A. The slurry is deposited onto the vibrating screen346, where the food granules proceed down the food slurry channel 348towards the right side of the drainer, as seen in FIG. 15A. The foodslurry channel is bounded on its upper surface by the top wall 350.Intake port 352 is seen as the opening in the upper portion of the foodslurry channel, and water drain space 354 extends along the underside ofthe vibrating screen 346. Water drains from the food granule slurry intothe water drain space, where it collects in water reservoir 356. Waterthen proceeds out water exit port 358. The food granules which havereduced water content, proceed out the food granule exit 362, and intothe drying apparatus. A support structure 360 forms the frame upon whichthe vibrating drainer is mounted. A vibrating motor 364 is seen on theunderside of the water drain space, and a water level sensor 366 extendsinto the water reservoir to enable the shut down of the vibratorydrainer if the water level should rise too high, for example, in a casewhere the water exit port becomes clogged. Right upper support strut 369is seen in the upper left portion of FIG. 15A, and right lower supportstrut 368 is seen on the left side of FIG. 15A.

FIG. 15B shows an end view of the vibratory drainer 300. In this view,the intake port 352 is seen at the top of the figure, with the top wall350 extending below that level. The left upper support strut 370 and theleft lower support strut 371 may be seen at the right edge of FIG. 15B.Further, the food granule exit 362 is seen at the center of FIG. 15B,and the water reservoir 356 and water exit port 358 are seen at thelower portion of FIG. 15B. A support structure 360 is seen on eitherside of the vibratory drainer and supporting the structure.

A remarkable drying effect may be achieved pursuant to the presentinvention, and in an efficient manner. In FIG. 14, the rotary dryer 32is provided with a cooked slurry of food granules from vibratory drainer300 (see FIG. 1 and FIGS. 15A and 15B). The food granules from thevibratory drainer proceed into entry station 226 (FIG. 14) where anyremaining water is drained from the slurry through drain line 36. Thisexcess water is recirculated in the recirculation cycle of theinvention.

The food granules are provided to the body of the rotary dryer wherethey are dried as they proceed into the various heat zones of the dryer.The heat zones that may be seen in FIG. 14 are the first heat zone 268,the second heat zone 270, the third heat zone 272, and the fourth heatzone 274. The heat zones may be regulated to various temperatures forvarious types of drying, depending upon the food particle to be dried(whether it is a cereal grain, a parboiled rice, a short grain rice,etc.) and the temperature of each zone may be regulated to achieve themaximum drying effect for the minimum amount of energy consumption ofthe dryer. Four separate burners 222 are provided, one to each heatzone, and blower fans 56 recirculate heated air from the main dryingchamber through the baffle plate 234 into the rotating barrel, and theninto the recirculation duct 232 and then eventually back into the dryingchamber (see FIG. 15). As cooked food granules 238 proceed through thebody of the dryer, (in the direction of the arrows seen in FIG. 14)their moisture content is reduced. Exhaust fan 216 is provided at theupper end of the rotary dryer to provide a positive air current flowalong the path of the food particles being dried. Dried food granules218 emerge from the distal end of the rotary dryer.

In FIG. 15, a cross-sectional view of the rotary dryer is seen. Barrel230 is rotated about central axle 224. Line 16A (FIG. 14) forms thecentral axis about which the barrel 230 rotates (see FIG. 15). The foodgranules proceed along the inner surface of the barrel 230. Air flowsfrom the inner portion of the barrel in drying zone 244 out through thedamper 236 and into the recirculation duct 232, where it is circulatedback into blower fan 56, and provided through baffle plate 234 back intothe drying zone 244. Thus, the air is provided in a circular path aboutwhich drying of the food granules may take place. Burner 222 is seen inFIG. 15 as providing a heat source for heating the circulating air. Alower housing 242 and lower damper 240 may be seen in FIG. 15. Damper236 and blower 56 and baffle plate 234 each may be adjusted to provideappropriate air speed through the rotary barrel.

The air speed at baffle plate 234 is typically less than the air speedwithin the rotating barrel 230, and the air speed is preferably in therange of 2000 to 3500 feet per minute within the rotary barrel. Thespeed of the air is increased upon entry into the rotating barrel due toits passage through perforations in the rotating barrel.

FIG. 16 shows barrel assembly 276 which forms a major component of therotary dryer. Beginning at the left of FIG. 16, motor 220 is seenattached to central axle 224, and it provides rotational torque to theaxle. Front end housing 374 forms the reservoir into which the wet foodgranules proceed from the entry station 226. Food granules proceed alongthe barrel. The barrel is preferably comprised of wire mesh ofsufficiently close spacing such that the food particles will not passthrough the mesh, but air and water may freely pass through such mesh.Dryer 32 may be positioned at a slight downward incline from the entryend to its exit end to facilitate the movement of rice.

A rear bearing 258 is held by support 264. Central axle 224 is securedto the motor 220. The motor 220 provides rotational motion to centralaxle 224. A housing 264 supports the motor assembly.

The rotary dryer is used for initial drying of the product and theresidence time of a rice grain in the rotary dryer typically is in therange of approximately 2 to 7 minutes, preferably about 3 minutes. Theair volume used in the rotary dryer may be as little as 3,000 or asgreat as 7,000 cubic feet per minute. The temperature of the airtypically is in the range of between 250° F., and 400° F., preferablyabout 350° F., although it will usually vary in different zones.

FIGS. 16A and 16B show a closeup and detailed view of the barrelassembly which forms the inner rotating portion of the rotary dryer seenin FIG. 14. In FIG. 16A, food granules which exit the vibratory drainerproceed into the entry station 226 as seen at the left side of FIG. 16A.Drain reservoir 412 receives excess water from the food granules afterthey are deposited into the rotary dryer, and excess water passes alongto drain line 36 as seen in the lower left portion of FIG. 16A. They aredeposited into the body of the rotary dryer, where a central axle 224 isturning, causing the barrel 230 to rotate on the axis of the centralaxle 224. Spiral flights 386 and 388 are seen at the left side of FIG.16A. Food granules, when they first enter the rotary dryer, are in theform of wet globules which must be moved along within the rotary dryerby physical means to flash off the water. This lateral movement fromleft to right is provided by the spiral flights 386 and 388, as seen inFIG. 16A. Meanwhile, blower ports 376, 378, 380, 382, and 384 providehot air circulation input which passes through the rotating barrel ofthe rotary dryer, and then exits the rotary dryer by way of lower airintakes 406, 407, 408, and 409.

As the hot air passes over the food granules within the rotating barrel,water is removed from the food granules. When the food granules haveproceeded approximately halfway down the rotating barrel, the granulesencounter mixing roller 392, which is fixedly mounted near the exitpoint of the rotating barrel, at the right side of FIG. 16A. The mixingroller 392 also rotates, which provides a working action of fingers 390,which are mounted upon the mixing roller 392. The fingers 390 help toloosen up and "fluff" the food granules (particularly in the case ofrice), and they assist in the drying of the rice in the latter stage ofthe rotary dryer.

Once the rice or other food granules are sufficiently dry, they proceedto the far right end of the barrel 230, where they encounter adjustablelip plate 400. This plate may be seen at the far right portion of 16A,as a small projection which extends up from the lower right edge of therotating barrel. In the case of rice, the preferred method ofdetermining retention time of the rice in the dryer is to allow the riceto remain within the rotating barrel until the rice is dry enough, andtherefore light enough in weight, such that the action of the rotatingbarrel will make the rice "hop" over the adjustable lip plate 400. Inthis way, the adjustable lip plate acts as a hurdle over which the ricewill bounce once it has become light enough, due to the action of therotating barrel 230. After the food granules have passed from the barrel230, they enter the collection zone 403. Collection zone 403 is definedby the end housing 394, which forms its periphery, and the food granulesproceed down through the food granule exit vent 396.

FIG. 16B shows an end view of the rotating barrel as seen along lines16B as seen at the right margin of FIG. 16A. In FIG. 16B, an innerbearing 398 may be seen at the center of the rotating barrel 230. Uponthis bearing, is the rotating central axle 224 which comprises fourspokes 404 extending at right angles out from the central axle.Adjustable lip plate 400 is seen releasably mounted upon the end of thebarrel 230. This lip plate provides the "hurdle" over which foodgranules may be required to bounce in order to exit the rotary dryer.The lip plate may be adjusted, by simply removing it and replacing itwith a lip plate of a different internal diameter, which would provide aslightly lower or higher "hurdle" for the food granules to bounce overupon exit from the barrel.

There are numerous variables in the drying of rice. Variables include,first, the amount of hydration of the rice as it enters the rotarydryer. Second, the velocity of the air in the rotary dryer. Third, thetemperature of the air within the rotary dryer. Fourth, the rotationspeed of the barrel 230. Fifth, the suction of the air laterally fromleft to right. Sixth, the size, shape, and type of the food granule orrice product being dried in the rotary dryer. Seventh, the adjustablelip plate at the end of the barrel, which may be raised or lowered toincrease or decrease the residence time of the food granules within thebarrel. Each of these variables may be adjusted for the most efficientdrying operation pertaining to that particular type of food granule, andthe particular type of processing desired.

Rotational speeds of the barrel of less than one cycle per second arepreferred. The rotary dryer of the present invention provides thecapability to partially dry the surface of the wet food granules orgrains, which aids in maximizing the puffing of the final product.Further, the rotational speed of the barrel is relatively low, and therice preferably is not subjected to large amounts of g forces as in someprior art methods. In this invention, rice is not "plastered" to theinner wall of the rotating barrel in a high speed spin, but instead issubjected to less than one g of force radially directed from the shafttowards the wall of the rotating barrel.

For some applications, it may be desirable to provide variation in thetemperature of the heat zones within the rotary dryer. For example, inthe first heat zone, seen as first heat zone 268 in FIG. 16A, the airthroughput may be very high, with a relatively high temperature toprovide a more desirable rice product. The temperature variations alongthe barrel 230 will provide different degrees of product uniformity, anddifferent amounts of puffing to create the type of product desired.

In the drying of the food granules in the present invention, a typicalbed dryer and vertical dryer may be used, both of which are known in theart for drying cereal grains such as rice. In the drying of cerealgrains, such as rice, the object is to "set" the product, that is, togive the rice grain a good characteristic for the consumer. It isdesirable to "freeze" the rice in a swelled state, by drying it andproviding a swelling effect of the water within the rice grain duringdrying. Further, a puffing effect is desirable whereby water providespockets of steam within each rice kernel, expanding the grain of rice,to provide appropriate texture and desirable qualities for the consumer.

In a bed drying operation, as indicated by reference numeral 14 in FIG.1, the temperature is typically between 275° F. and 325° F., preferablyabout 300° F. A bed dryer is a belt dryer whereby rice is providedthrough the dryer on a bed or belt, and air is blown either down ontothe belt or up through the bottom of the belt. In such bed dryingoperations, the air velocity is much lower than the rotary dryingoperation, typically about 300 feet per minute. In the bed dryingoperation, a residence time of approximately 5 to 15 minutes, preferablyabout 10 minutes is used.

For certain types of cereal grains, and in particular for quicklyrehydrating rices, a vertical dryer, as indicated by reference numeral15 in FIG. 1, may be used to greatly reduce the moisture content of ricedown to a level as low as 6% water. For example, a vertical dryer may beused to provide grain with a residence time in the dryer ofapproximately two hours. The principles of bed and vertical drying areknown by persons skilled in the art.

The Efficient Use of Water in the Present Invention

In the processing of the food granules, water is recirculated and reusedso that the amount of water used in the processing of food granules isminimized, i.e., the amount of water used and/or excreted per pound offood processed is kept at a low level.

FIG. 17 shows the water pathways in the present invention and, inparticular, shows the recirculation of water in the present invention inreducing the amount of water consumed and excreted. As shown in bothFIGS. 1 and 17, in the cooking of food granules, heat exchanger 24provides heat to and absorbs heat from the various hot water and steamlines in the processing system. For example, fresh water inlet 26provides water into the heat exchanger 24, and boiler 28 is providedwater from inlet 52. Steam from the boiler may be provided to the heatexchanger along steam line 49, and steam line 47 extends between theheat exchanger and the boiler 28.

The water food granule slurry which proceeds along conveyor line 38 intothe vibratory drainer 300 is drained. The drained "used" or recirculatedwater is provided along drain line 36 to a point at which it is mixedwith steamer drain line 37, which comprises "used" water from thesteamer. These two lines are mixed (as seen in the upper left handcorner of FIG. 17) into a combined drain line 39. This combined drainline is provided to filter 278 as seen in FIG. 17, and also as seen inFIG. 1.

The filter essentially provides a macroscopic filtering of foreignparticles from the water, and the water is then provided to alternateroutes. It may be provided along exit line 120 where it may be valved toone of two places. It can proceed along drain line 121, or it mayproceed along recirculated water line 30 to be fed back into the steamcooker for reabsorption by the food granules and used in the cooking offood granules at steam cooker 90. If the recirculated water is fed alongdrain line 121, it may be drained out of the system (into the sewer)from drain 29. As another pathway, the recirculated water may be sentthrough valving along the path of dispenser line mixture 34, where itmay be reinjected into a bucket 27 for reabsorption by uncooked foodgranules as they proceed towards the steam cooker.

Furthermore, the water that drips from buckets 27 upon release of thefood granules from the buckets along the conveyor 50 is collected underthe conveyer 50 and provided along drain line 41 to steamer drain line37, in a similar manner as the water which is drained along drain line36. Again, a portion of the "used" water may be drained away from thesystem at drain 29, while some of it is recirculated back into thebuckets 27. Further, hot water line 18 provides hot water from the heatexchanger 24 to the steam cooker 90.

In FIG. 1, the amount of water provided to bucket 27 through dispenserline mixture 34 will depend upon the steeping conditions of thatparticular batch. For certain food granules, a greater mixture of freshwater may be required to prevent gluing of food particles together andto facilitate the free flow of food granules through the system. Formaximum water conservation, however, the amount of water provided at hotwater line 18 is kept to a minimum, while the recirculated water line 30is allowed to provide a maximum amount of recycled water, thereby aidingin the overall conservation of water.

Further, fresh hot water is provided from the heat exchanger 24 throughhot water line 18 to either the steam cooker 90 or to the prewasher 12.Hot water line 18 provides hot water along hot water line 99 to thesteam cooker 90. The prewasher 12 may use water which is warm, hot, orcold, but preferably using the Jiff-Wash system described previously, acold water rinse is used. A cold water line is available to theprewasher 12, but is not shown in FIG. 17.

If desired, hot water input 22 may provide hot water to the prewasher,either for use in prewashing or for cleaning the apparatus. Conveyor 16transports food granules through the presteamer 20, where they aredeposited into buckets 27, and there they receive the dispenser linemixture 34. Boiler 28 provides steam along steam line 49 to both thesteam cooker 90 and to the heat exchanger 24. Steam is provided from theboiler to the presteamer 20 along steam line 49 as seen in FIG. 17.

Further, steam cooker 90 may excrete "used" recirculated water 37, whichproceeds along steamer drain line 37, to be filtered and then ultimatelyeither reused or drained from the system. One of the key features ofthis invention relative to the abilities of reuse water efficiently isthe discovery of the water clarity that is achievable for the waterexiting the cooker at line 37. It is believed that this is achieved as aresult of two things primarily; the use of the pre-steamer step and theoverall optimal supply of water in a proper temperature and volumemanner so as to avoid the leaching out of loose starch molecules byproviding water in quantities that are coordinated to roughly the amountthat the rice can absorb at a particular point in the process. Thetemperature maximum is important because if it is too high, then starchdamage (i.e., the release of free starch and the undesirable gluingeffect) may occur.

The food granule slurry departs the steam cooker 90 along conveyor line38, to the rotary dryer 32. Vertical dryer 15 and bed dryer 14 are alsoseen in FIG. 17, with dashed lines to indicate that they are optional,and not required in the present invention.

Using the recirculation in the present invention, the amount of waterused per pound of rice produced may be greatly reduced. In theoperations of the present food processing system, the water content ofrice as it exits the steam cooker is typically between about 50 to 60%water. Rice is typically about 40% to 50% water as it comes out of thebuckets 27 and proceeds to the steam cooker. After cooking, and in thedrying stage, the percentage of water after the first stage of drying(rotary drying) is about 20% water, but this percentage will varydepending upon the product.

The present system results in the amount of water applied or excretedbeing minimized, to a level of less than about 3 to 1 by volume.

If the rice is provided to a bed dryer following rotary drying, thewater content may be reduced to about 12%. If further drying is requiredor desirable, the water content of the rice may be reduced in a verticaldryer to as little as about 6% water. Different rice products willutilize different percentages of water and it should be noted that thegreater the amount of moisture reduction achieved, the more expensivethe drying process will be in terms of energy consumption.

Obviously, numerous possibilities are available for the recirculatedwater in the present invention, and the most efficient use ofrecirculated water will depend upon the cooking conditions, the type offood granules processed, and in the case of rice, will depend upon thevariety of rice, and whether it is short grain rice, long grain rice,parboiled rice, etc.

For example, the examples below use only three zones for drying (i.e.,zone 1, zone 2 and zone 3; wherein zone 1 is the closest to the entranceof the dryer, zone 2 is next, and zone 3 is the furthest from the dryerentry point). Additional drying zones might be used in otherembodiments. Also, the air velocities in the drying zones are in therange of about 2500-3500 feet per minute, preferably about 2500-2800 atthe air blower 56, and 3000-3500 feet per minute within the rotatingbarrel.

EXAMPLE 1

The following example provides the preferred processing conditions forpracticing the present invention using precooked, milled, parboiled,white long grain rice as the food granule to be cooked. Of course, theseprocessing conditions may be varied for different varieties of rice orfor food granules which are not cereal grains, such as vegetables orother food granules. Further, the specifications below may be variedeven for milled white long grain rice if certain other characteristicsare desired in the final end product.

In the washing step, it is preferred in this example that the washingoccur for a period of about 30 seconds, with the ambient temperature ofthe washing water at approximately 25° C. The moisture range of the riceafter washing is in the range of approximately 16% to 18% water.

In the presteaming step, a 15 minute pre-steam is provided to the rice,with ambient pressure, to achieve a moisture range of the rice ofapproximately 22% to 25% water.

The steeping step occurs for approximately 15 minutes as the rice movesalong the conveyor in buckets 27, using water which is at a temperatureof about 80° C. The moisture range achieved during the steeping is arange of approximately 56% to 58% water. The charge of rice used in eachcontainer is approximately 15 kilograms, using about 22 liters of waterin each bucket for the steeping step.

In the steam cooker 90 (see FIGS. 2A-2C), the rice is cooked forapproximately 15 minutes at ambient pressure, achieving a moisture rangeof about 59% to 60% water.

After steaming, the rice is transported in an aqueous environment forabout 30 seconds using water of ambient temperature (about 25° C.), andachieves a moisture content of about 62% to 63% water. The transportoccurs by pumping to a dewatering device (vibratory drainer). The riceis transferred to the vibratory drainer, and into the rotary dryer. Thetemperature of the first zone is about 250° C., while the temperature inthe second and third zones is about 195° C. The air velocity is avariable that may affect drying temperature. The retention time of therice within the barrel of the rotary dryer is about 21/2 minutes. Thisis the time which elapses between the time the rice enters the barreland the rice exits the barrel by bouncing over the adjustable lip plate400 at the distal end of the barrel within the rotary dryer. Themoisture range of the rice as it exits the rotary dryer is at a level ofabout 20% to 22% water.

After the rice exits the rotary dryer, it proceeds to a bed dryer for adrying time of about 5-7 minutes. This drying occurs at a temperature ofabout 100° C., and the rice achieves a moisture range, after drying, ofabout 9% to 11% water. The end product is a precooked rice requiringabout 5 minutes to prepare.

The conditions in these examples are provided as examples only, and theyshould not be construed to limit the invention in any way.

EXAMPLE 2

In a second example, a five minute, precooked, milled, white, long grainrice is used as the product to be cooked. In order to prepare the rice,the temperature, time, and moisture ranges provided by below arebelieved to be preferable. Nevertheless, different varieties of rice,and different processing conditions may be employed to achieve a productwith different characteristics.

First, parboiled rice is provided, and is prewashed for approximately 30seconds using water which is ambient temperature, to achieve a moisturerange of rice which is approximately 16% to 18% water. The rice is thenpresteamed for about 10 minutes. This achieves a rice with a moisturecontent of about 22% to 23% water. The rice is then steeped in buckets,as disclosed herein, for about 10 minutes, at approximately 80° C. Themoisture range achieved after steeping is approximately 50% to 52%. Therice is then steam cooked for about 10 minutes in the preferred steamcooker of the present invention. In this case, the steam cooker would bethe preferred steam cooker as seen in FIGS. 2A-2C. The rice is thensteam cooked at 150° C., and achieves a moisture level of about 53% to55% water. The rice is then transported in a water slurry, whichrequires about 15 seconds, at ambient temperature, achieving a moisturelevel of about 58% to 59%.

The rice is then provided to a rotary dryer for two to three minutes atan air temperature which varies between 195° C. and 250° C. In therotary dryer, zone 1 is operated at 250° C. (the zone nearest the dryerentrance), and zones 2 and 3 are operated at 295° C., with totalretention time in the dryer of about 2.5 minutes. The rice is then at amoisture level ranging from 22% to 25%. The rice is then provided to abed dryer for 5 to 7 minutes, at a temperature of about 100° C. Themoisture level achieved after drying in the bed dryer is about 9% to11%. As a final product, a 5 minute, precooked, white instant rice isproduced which is capable of a five minute simmer cook by the consumer.

EXAMPLE 3

In a third example, a starting material of milled, white, long grainrice is provided for processing. It may be processed in the followingexample to produce an instant, white, long grain rice with a preparationtime of about 7 minutes, and with a firmer cooked texture which ischaracteristic of European-style marketed rices. First, milled, white,long grain rice is prewashed, as described previously, for 30 secondsusing water which is at ambient temperature (about 25° C.). The ricethen achieves a moisture range between about 16% and 18% water. The riceis then steam cooked for approximately 10 minutes at ambient pressure,which results in a moisture range between 22% and 23% water. That stepis followed by steeping of the rice for 10 minutes using water of 80° C.(176° F.). A moisture level of between 50% and 52% is achieved. Thetemperature should be controlled during the steeping, and a 15 kilogramcharge of rice is utilized with a 22.5 liter quantity of water. The riceis then steam cooked for 10 minutes at ambient pressure to achieve amoisture range of between 53% and 55% water.

The rice is then transported from the steam cooker towards the dryingapparatus for a period of time which is about 30 seconds, using ambientwater temperature of about 20° C. to 25° C. The moisture range of therice at this point in the processing is between about 58% and 59% water.

In this embodiment, a slow drying process is preferred, to produce acooked texture which is characteristic of European-type rices. Thedrying proceeds for about 30 minutes at approximately 75° C., to achievea moisture level of between 9% and 11%. The rotary dryer is used, but isnot required for this end product. The texture produced by this methodrequires a low drying temperature, as for example, 75° C. as provided inthis particular example. The product produced is an instant, white, longgrain rice with a preparation time of about 7 minutes and with a firmercooked texture.

EXAMPLE 4

In the fourth example, the rice cooked is a brown, long grain rice, andit produces an end product which comprises an instant, brown, long grainrice, with a preparation time of about 10 to 12 minutes. Further, ifsofter texture is desired, a 12 minute preparation time is recommended,however, this example provides a rice with a preparation time that ispreferably about 10 minutes.

First, the rice is prewashed for 30 seconds with an ambient watertemperature, to produce a moisture content of the rice between 14% and16%. The rice is then presteamed for 18 minutes at ambient pressure. Amoisture level of about 18% to 20% is achieved.

The rice is then steeped for 18 minutes at 80° C. (176° F.). A moisturerange of between 42% and 45% is achieved after the steeping step. Therice is then steam cooked for 18 minutes at ambient pressure, to achievea moisture range of 50% to 55% water.

The rice is then transported, by way of water, for about 30 seconds outof the steam cooker and to the drying apparatus. The moisture range atthis point is 58% to 59% water.

The rice is then dried in the rotary dryer, using dryer temperatures inzone 1 (the zone closest to the inlet of the dryer) of 230° C. Zone 2 isat a temperature of about 195° C., and zone 3 is also at a temperatureof about 195° C. The moisture level of the rice after rotary drying isabout 15% to 18% water.

The rice is then provided to a bed dryer for a drying time of between 5and 7 minutes at 100° C. (212° F.). The moisture content of the riceafter bed drying is between 9% and 11%. The product of this particularexample is an instant, brown, long grain rice with a preparation time bythe consumer of about 10 to 12 minutes.

Modifications of the apparatus and methods disclosed in this patentapplication could be conceived by a person skilled in the art, withoutdeparting from the spirit or scope of the invention. For example, it iscontemplated that the present invention could be utilized whereby adifferent number of heating sections in the rotary dryer or a differentconfiguration of the cooking segments in steam cooker 90 may beestablished.

It is anticipated that different types of steam cookers could beestablished which utilize either vertical means of feeding food granulesby way of gravity inducement, or a horizontal method might beestablished whereby food granules may be cooked and fed through in ahorizontal manner. Further, it is obvious that variations could occur inthe method and apparatus of recirculating water in the present inventionto most advantageously and efficiently utilize the least amount of inputwater and excrete the least amount of waste water. The present inventionis not limited to the disclosure in this regard, and other arrangementscould be easily conceived. Further, the temperatures, pressures, andcooking conditions disclosed herein are disclosed as the preferred andalternate embodiments, but cooking could occur using temperatures,pressures, and/or methods that are not disclosed in the presentspecification, but still fall within the scope of this invention.Additionally, although the disclosed apparatus and methods have beendescribed primarily for use with rice, these apparatus and processes aresuitable for use with other food products, as well. The presentdisclosure is intended to cover all such modifications as fall withinthe scope of the appended claims, including equivalents.

What is claimed is:
 1. A method of drying a food granule slurry which comprises water and wet food granules, comprising:advancing the food granules within and in a direction along the length of a perforated rotating barrel, the barrel having separately controllable temperature zones therein; blowing air past the food granules along a path that passes through perforations in the barrel, across the inner space within the barrel, and exits through perforations in the barrel; and controlling the residence time of the food granules in the rotating barrel with a food granule retention device operatively coupled adjacent an exit of the rotating barrel, the retention device configured to retain the food granules in the rotating barrel until the food granules are dried to a predetermined moisture content.
 2. The method of claim 1, further comprising maintaining the air in each temperature zone at a different temperature.
 3. The method of claim 1, wherein further comprising swelling the food granules during drying.
 4. The method of claim 1, further comprising inclining the rotating barrel to facilitate advancement of the food granules along the length thereof.
 5. The method of claim 1, wherein the flow of air blown past the food granules is adjustably regulated by dampening to achieve optimum flow rates for a particular processing condition, a particular end product, or both.
 6. The method of claim 1, wherein the retention device comprises an adjustable hurdle.
 7. The method of claim 1, additionally comprising further drying the food granules in a dryer selected from the group consisting of a bed dryer and a vertical dryer.
 8. The method of claim 1, additionally comprising maintaining a temperature of between about 250° F. to about 400° F. in the temperature zones.
 9. The method of claim 1, further comprising recirculating the air exiting the rotating barrel.
 10. The method of claim 1, further comprising advancing the food granules along the length of the rotating barrel with a food granule advancer disposed therein.
 11. The method of claim 1, further comprising mixing the food granules with projections extending from a rotating shaft disposed within the rotating barrel.
 12. The method of claim 10, wherein the food granule advancer comprises a plurality of spiral flights disposed on an interior surface of the rotating barrel.
 13. The method of claim 1, wherein the air velocity in the rotating barrel is between about 2000 feet per minute and about 3500 feet per minute.
 14. The method of claim 1, further comprising puffing the food granules during drying.
 15. The method of claim 1, additionally comprising, before advancing, separating excess water from the wet food granules.
 16. The method of claim 1, wherein the rotating barrel applies a centrifugal force of less than about 1 g upon the food granules.
 17. The method of claim 1, wherein the food granules entering the barrel have a moisture content of about 50% to about 65% by weight.
 18. The method of claim 1, wherein the food granules entering the barrel have a moisture content of about 50% to about 55% by weight.
 19. A method of drying a food granule slurry which comprises water and wet food granules, comprising:simultaneously applying a centrifugal force to the food granules and causing them to advance in a direction substantially normal to the centrifugal force, by rotating a perforated barrel in which the food granules are held, the barrel having separately controllable temperature zones therein; advancing the food granules substantially normal to the centrifugal force with a food granule advancer disposed within the barrel; blowing air past the food granules in a direction substantially parallel to the centrifugal force to dry the granules; and controlling the residence time of the food granules in the rotating barrel with a food granule retention device operatively coupled adjacent on exit of the rotating barrel, the retention device configured to retain the food granules in the rotating barrel until the food granules are dried to a predetermined moisture content.
 20. The method of claim 19, further comprising maintaining the air in each temperature zone at a different temperature.
 21. The method of claim 19, further comprising inclining the rotating barrel to facilitate advancement of the food granules substantially normal to the centrifugal force.
 22. The method of claim 19 wherein the retention device comprises an adjustable hurdle.
 23. The method of claim 19, additionally comprising initially separating excess water from the wet food granules.
 24. The method of claim 19, wherein the centrifugal force is less than about 1 g.
 25. The method of claim 19, wherein the food granule advancer comprises a plurality of spiral flights disposed on an interior surface of the rotating barrel.
 26. The method of claim 19, further comprising mixing the food granules with projections extending from a rotating shaft disposed therein.
 27. The method of claim 19, further comprising recirculating the air exiting the rotating barrel.
 28. The method of claim 19, additionally comprising further drying the food granules in a dryer selected from the group consisting of a bed dryer and a vertical dryer.
 29. The method of claim 19, additionally comprising maintaining a temperature of between about 250° F. to about 400° F. in the temperature zones.
 30. The method of claim 19, wherein the food granules comprise rice.
 31. The method of claim 19, wherein the air velocity in the rotating barrel is between about 2000 feet per minute and about 3500 feet per minute.
 32. The method of claim 19, further comprising swelling the food granules during drying.
 33. The method of claim 19, further comprising puffing the food granules during drying.
 34. The method of claim 19, wherein the food granules entering the barrel have a moisture content of about 50% to about 65% by weight.
 35. The method of claim 19, wherein the food granules entering the barrel have a moisture content of about 50% to about 55% by weight.
 36. A method of drying a food granule slurry which comprises water and wet food granules, comprising:separating excess water from the wet food granules; advancing the food granules through a rotating barrel from a proximal end of the rotating barrel to a distal end of the rotating barrel, wherein the rotating barrel including a plurality of spiral flights disposed on an interior surface of the rotating barrel for advancing the food granules to the distal end of the rotating barrel; mixing and evenly distributing the food granules within the rotating barrel, wherein the rotating barrel includes a rotatable shaft disposed therein, the rotatable shaft having projections for mixing and distributing the food granules; blowing heated gas upon the food granules in separate, controllable temperature zones disposed along the path of advancement of the food granules; controlling the residence time of the food granules in the rotating barrel with an adjustable hurdle coupled adjacent the distal end. 